This invention relates to a brake actuator for use in a vehicle having air brakes, and is of the same general type as the actuator disclosed in U.S. Pat. No. 3,789,737, owned by the assignee of the present invention.
As is well known to those skilled in the art, brake actuators for heavy duty vehicles equipped with air-actuated brakes are located in an extremely adverse environment on the underside of the vehicle, where they are exposed to road dirt, dust, salt, and other contaminants. Furthermore, most existing actuators are designed so that this contaminated atmospheric air is drawn into the actuator upon brake release, thereby damaging the walls of the housing and the seals used within the actuator. Ultimately, of course, the corrosive nature of these contaminants may damage the brake mechanism itself and result in a brake failure. For this reason, it is desirable to design a brake actuator in which the actuator is automatically purged of contaminants on brake release, so that may contamination which might be drawn into the actuator during normal operation of the latter is automatically purged periodically. Furthermore, any type of actuator must be designed so that the actuating piston used within the actuator may articulate with respect to the actuator housing, as many brake actuators, particularly the type used to actuate air-actuated disc brakes, require articulating movement of the piston.